The purpose of the Medical Studies Database System (MSDS) is to provide a computerized system that facilitates data handling functions with a high degree of automation that minimizes data collection errors and computer programming and provides forms-tracking, data updating with automatic audit-trail and user-friendly data retrieval. The methodology involves: 1) Entry of medical data from data collection forms onto Hewlett Packard 2647A Intelligent Terminal screens which mirror the data collection forms; 2) The transfer of the data to a data base management system (DBMS), Hewlett Packard's Image, on an HP-1000 minicomputer under the RTE 6/VM operating system; 3) A forms-tracking system which records the validity status of the data; 4) Dictionary driven range and relational validity checks; 5) Easy-to-use time-oriented subsetting and retrieval utilities.